Fasteners are used for attaching upholstery trim boards to vehicle body panels. A trim board is attached to a vehicle body panel by placing the former on the latter and inserting a fastener into their respective attachment holes. Patent document 1 discloses a fastening member for fastening an upholstery component of an automobile to a panel component. The fastening member includes a grommet and a pin.
The grommet disclosed in Patent document 1 has a brim portion having an opening, a cylindrical base portion projecting downward from the brim portion, a thin hinge portion projecting downward from the base portion, and four thick leg pieces formed under the hinge portion. Each leg piece has a guide portion that projects from an inner surface of the leg piece toward the center line of the grommet. By receiving the pin being pushed in through the opening at the guide target portions, the leg pieces are expanded, and the hinge portion are bent.